Resilient retainer for drill steel



May 3, 1960 RESILENT RETAINER FOR DRHJL STEEL Application September 24,1958, Serial No. 763,052

9 Claims. (Cl. 279-195) This invention relates to percussive tools suchas rock drills, and more particularly to a retainer for preventingaccidental removal of the drill steel or working implement from thedrill.

it is common practice to provide the drill steel with a collar and therock drill with a latch movable into and out of the path of the collar,the latch being pivotally mounted on a pin which in turn is rigidlysupported by the front head of the drill. The latch, when effective,receives blows of percussion from the drill steel and usually transmitsthem to the supporting pin and front head. The rock drill parts whichreceive and transmit such impacts are subjected to frequent breakage.

An object of this invention is to absorb the shocks transmitted throughthe retaining latch and therefore to protect the parts from breakage andprolong the life of the rock drill.

Another object is to protect the operator against such shocks.

A further object is the provision of a shock absorbing retainer devicewhich is convenient to manipulate, inexpensive to manufacture, simple inconstruction and convenient to assemble and disassemble.

A feature of this invention is a resilient bushing, comprising a body ofrubberlike material interposed between the hub portion of the latch andthe supporting pin, the bushing having a tendency at all times tomaintain the hub in coaxial relation with the pin but being yieldableunder stress to permit the axis of the hub to be olfset parallel to theaxis of the pin.

ther objects and features of this invention will appear from thedescription which follows.

in the accompanying drawings which show one form of this invention:

Fig. l is a longitudinal section of the front portion of a rock drillembodying this invention, showing also the rear portion of the workingimplement;

Fig. 2 is a fragmentary elevational view of the front head, looking fromthe right of Fig. 1;

Fig. 3 is a cross-section looking along the line 3-3 of Fig. 1, lookingrearward as indicated by the arrows;

Fig. 4 is a side elevation of one of the washers for the retainer bolt;and

Fig. 5 is an end view of said washer looking from the right of Fig. 4.

Referring to Fig. l, the illustrative rock drill is of the type known asa demolition tool and delivers hammer blows to a working implement ordrill steel 11 inserted into the lower or front end of the drill. Thedrill comprises the usual cylinder 12, only the front portion of whichis shown, which receives a reciprocating hammer piston 13. The cylinderis sealed at its front end by a front cylinder washer 14 which connectsthe cylinder to the front head 15. The front cylinder Washer serves tocentralize the front head with respect to the cylinder and also toprovide a seat for an anvil block 16 slidably mounted in the frontcylinder washer. The anvil block atom ice

receives the blows of the hammer piston 13 and transmits them to theworking implement 11.

The working implement has a hexagonal shank 17 slidably fitting ahexagonal opening 18 in a chuck bushing 19 which is rigidly supported inthe front head, for example, by means of a press fit within a bore 26 inthe front head 15. Adjacent the shank 17, the implement has a collar 21,which normally seats against the front extremity of the chuck bushing 19to provide a positive stop limiting rearward movement of the implement11. In front of the chuck bushing 19, the front head 15 is provided witha counterbore 22 which surrounds the collar 21 and permits reciprocationthereof.

Retaining means are provided for preventing the working implement 11from being ejected from the front head. To support such retaining means,the front head 15 is provided with a pair of lateral ears 23 definingtherebetween a longitudinal slot 24 open at the front extremity of thefront head. A latch 25 is disposed in the slot to cooperate with thecollar 21 on the working implement.

The latch has a hub portion 26 the ends of which snugly fit the sides ofthe front head slot 24 with lapping engagement as shown in Figs. 2 and3. Extending rearwardly from the hub portion is a handle 27 the rear endof which projects beyond the slotted part of the front head and isexposed for convenient manipulation. Extending radially inward from thehub portion, and approximately at right angles to the handle, is a stoplug 28. As seen in Figs. 1 and 3, the stop lug is interposed in the pathof the implement collar 21 and prevents withdrawal of the implement fromthe front head when the latch is in the position shown. Between thehandle and lug the latch has an inclined cam face 29. Cooperating withthe cam face is a plunger 31 mounted in a bore 32 in a lateralenlargement 33 on the front head 15. A spring 34 in the bore presses thepin forwardly, causing the front extremity of the pin to ride over thecam face 29 when the latch is turned about the axis of the hub 26.Normally, the plunger engages within a depression 35 in the latch toyieldingly lock the latter in the position shown in Fig. 1. When thehandle 27 is swung outward and forward, the plunger 31 comes out of thedepression 35 and rides over the cam face 29 and finally engages the lug23 to arrest further movement of the latch, after it has been turnedalmost ninety degrees from the position shown in Fig. 1. In suchofi-normal position, the lug 28 clears the collar 22 to permit removalof the working implement 11 from the front head 15 in a well-knownmanner.

The present invention resides in the means for pivotally supporting thehub portion 26 of the latch 25. Such means comprises a resilient bushing36 mounted in a bore 37 in the hub 26. The bushing comprises an outermetal sleeve 38, an inner metal sleeve 39, and an intermediateeylindrical body 40 of rubberlike material such as neoprene, bonded toboth sleeves and normally holding them in co-axial spaced relation. Asshown in Pig. 3, the metal sleeves are co-extensive in axial length withthe hub 26 and have rotative engagement at their extremities with thewalls of the front head slot 24. The body of neoprene, however, isrecessed or spaced as at 41 a little inwardly of the ends of the bushingand, therefore, is out of engagement with the front head walls 23.

The inner sleeve 39 has a rotating fit on a pivot pin or bolt 42 whichextends transversely of the front head slot 24. One end of the bolt isprovided with an integral head 43 while the other end is threaded forengagement with a nut 44. The bolt is supported rigidly in a pair ofsplit washers 45. As shown best in Figs. 4 and 5, each washer is offrustoconical shape and has a tapered pe-" ripheral surface, acylindrical bore 47 and a radial slot48 extending from the bore to theperiphery. The tapered peripheries engage respectively complementarytapered openings 49 formed in the ears 23 on opposite sides of thelongitudinal slot 24. As shown in Fig. 3," the'split washers, whenassembled, taper inwardly and the large ends have engagementrespectively with the nut 44 and the bolt head 43. Due to the radialslot 48, the washers are resilient and, upon tightening of the nut 44,are wedged into firm engagement with the front head recesses to firmlysupport the pivot pin 42 against any movement relative to the front head15.

In operation, the rock drill or demolition tool llii is normally heldwith the chuck bushing 19 pressing against the implement collar 21 andwith the front end of the implement 11 pressing against the rock orother material (not shown) being drilled. The hammer piston 13 deliversblows of percussion through the anvil block 16 to the implement 11.piston to reciprocate while the drill and implement are not pressedagainst the work, the implement 11 will be propelled toward the frontextremity of the drill. In the absence of any retainer, an accidentmight result. However, the forward motion of the implement is arrestedby the impingement of the collar 21 against the stop lug 28 on the latch25. As a result of such impingement or impact, the latch tends to turncounterclockwise as seen in Fig. l, but such motion is prevented by theengagement between the handle 27 and the outside of the radialenlargement 33 on the front head. The operator may inadvertently permitthe hammer piston to continue to reciprocate and thereby deliver impactsthrough the medium of the anvil block 16, implement shank 17 andimplement collar 21 to the stop lug 28. Such impacts cause stresses andstrains in the latch 25, the pivot pin 42 and in the front head ears 23which serve as bearings for the pin. The repetition of such strains hasa tendency to set up fatigue failure with the liability of breakage ofthe latch 25, pivot pin 42 or the front head cars 23, in the absence ofany means for counteracting or absorbing such shocks. Breakage of any ofthese parts could occur as a result of the operators failure to hold therock drill pressed against the implement, thereby permitting the latterto strike the latch as previously mentioned and also as a result of theoperators efforts to use the latch as a percussive means for pulling astuck implement out of a drill hole. In accordance with the presentinvention, the shocks are absorbed by the neoprene material 41which'permits the hub portion 2 6 of the latch to move laterally tooffset its axis relative to the pin 42. The recesses 41 at the ends ofthe rubber cylinder 40 provide spaces for the flow of rubber to permitsuch axial disalignment. While the invention permits relative lateral orradial movement between the latch 25 and the pin 42, it prevents suchmovement between the pivot pin 42 and the front head 15. Any tendencyfor the pinto become loose in the front head ears 23 as a result ofvibrationmay be offset by tightening the nut 44, thus taking up anylooseness and preventing lost motion which might otherwise result inwear and breakage at'the connections between the pivot pin and fronthead. 7

The resilient bushing 36 ,not only protects the rock drill apparatus asmentioned, but also lessens the shocks transmitted to the operator.

When the operator desires to change the implement V 11, he merely swingsthe handle 27 away from the front head with suilicient force to overcomethe yielding lock provided by plunger 31 and depression 35 until thestop lug 28 is removed from the path of the collar 22. During suchmovement, the hub 26 and outer sleeve 38 have a lapping engagement withthe walls of front head slot What is claimed is: V

l. A percussive tool comprising a front head adapted for the support ofa collared working implement, a manipulative latch pivotally movableinto andoutpof he If the operator permits the path of the implementcollar, a cylindrical pivot pin supported by the front head andextending transversely through said latch, nut and lock washer meansrestraining the pivot pin from movement relative to the front head andresilient means rotatably sleeving the pin for supporting the latch forfree pivotal movement about the pin and for limited movement of thelatch transversely to said pin.

2. A percussive tool according to claim 1, in which the means forsupporting the latch comprises a bushing having an inner cylindricalsleeve coaxial with the pin and an outer cylindrical sleeve coaxial withthe inner sleeve and fixed to the latch, and resilient means interposedbetween the inner and outer sleeves and bonded to them.

3. A percussive tool according to claim 2, in which the resilient meansis a cylindrical rubberlike body, said rubberlike body tending to holdthe sleeves in axial alinement but permitting disalinement under stress.

4. A percussive tool according to claim 3, in which the front head has alongitudinal slot to receive the latch, the side walls of the slothaving lapping engagement with the latch and the outer sleeve, and therubberlike body being recessed at its ends inwardly of the inner andouter sleeves and of the side walls of the slot whereby it is normallyout of contact with the latter walls and is adapted to flow axially atsaid recessed ends upon radial V compression thereof during movement ofthe latch transversely of the pin.

5. A percussive tool comprising a front head having a pair oflongitudinally extending ears defining a slot therebetween, a pivot pinsupported by the front head and extending transversely through said earsand slot, a manipulative latch in said slot having a hub portionsurrounding the pin and pivotally movable on the pin with the ends ofthe hub portion in lapping engagement with the sides of the slot, andresilient means interposed between the hub portion and pin to absorbshocks delivered to the latch, wherein the resilient means is a' unitarybushing comprising an inner cylindrical metal sleeve member sleeving thepin in rotative relation thereto, an outer metal sleeve membersurrounding the inner sleeve member in spaced coaxial relation theretoand received in said hub portion, and a cylindrical resilient bodyinterposed between and bonded to the inner and outer sleeve members, theends of the resilient body being recessed slightly inwardly relative tothe corresponding ends of the sleeves to allow for slight axialexpansion flow of the resilient body.

6. A percussive tool comprising a front head having a pair oflongitudinally extending ears defining a slot therebetween, a pivot pinsupported by the front head and extending transversely through said earsand slot, a manipulative latch in said slot having a hub portionsurrounding the pin and pivotally movable 0n the pin with the ends ofthe hub portion in lapping engagement with the sides of the slot, andresilient means interposed between the hub portion and pin to absorbshocks delivered to the latch, characterized by a pair of washers forsupporting the pin, said washers tapering toward each other and beingfitted within complementary tapered recesses in the front head ears.

7. A percussive tool according to claim 6, in which each washer has acylindrical bore and a radial slot extending rom the bore to the taperedperiphery, the cylindrical bore being clamped tightly about the pin uponmovement of the washers toward each other.

8. In a percussive tool having a percussively driven collared drillsteel slidably inserted in the front head of the tool and adapted toescape from the latter when driven unless blocked; latch means forresiliently blocking such escape, comprising a pin supportedtransversely of a slot having communication radially through the sidewall of the front head with the drill steel, a bearing member sleevingthe pin and comprising an inner cylindrical metal sleeve coaxial withand in bearing contact with the pivot pin, an outer cylindrical metalsleeve coaxial with the inner sleeve and in spaced relation thereto, anda cylindrical resilient body in the space between the sleeves and bondedto them; a latch member having a hub in which the bearing member isreceived, a lug ofiset from the hub, and a manipulative elongated armoffset from the hub in angular spaced relation to the lug, the latchmember having an operative pivoted position upon the pivot pin whereinthe lug projects through the slot into the downward path of fovement ofthe collar of the drill steel and wherein the elongated arm abuts theside area of the front head upwardly of the slot, and the resilient bodyaffording limited radial movement to the latch member relative to thepivot pin upon contact of the collar of the drill steel with the lug;and resilient detent means yieldingly maintaining the latch member inits operative position.

9. In a percussive tool of the character described, including a fronthead, and a drill steel adapted to be percussively driven in an outwarddirection relative to the front head; a pivot pin in the front head; alatch member pivotable into the path of movement of the drill steel soas to limit the extent of outward movement of the latter; and resilientmeans pivotally mounting the latch member to the pivot pin characterizedby a cylindrical metal sleeve member surrounding the pivot pin inhearing relation thereto; an outer cylindrical metal sleeve in coaxialspaced relation to the inner sleeve and fixed in the latch member; and acylindrical resilient body member substantially filling the spacebetween the sleeves and bonded to both.

References Cited in the file of this patent UNITED STATES PATENTS1,712,239 Wilhelm May 7, 1929 2.122516 Curtis et al. July 5, 19382,230,046 Curtis Jan. 28, 1941 2,272,202 Fish June 7, 1949 2,500,038Lear Mar. 7, 1950 2,720,401 Fuehrer Oct. 11, 1955

